In the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) (or Rel-8 or Rel-9) standard, single carrier-frequency division multiple access (SC-FDMA) is used as an uplink multiple access scheme. In the 3GPP LTE-A (for example, 3GPP LTE release-10) standard which is evolved from the 3GPP LTE standard, introduction of a clustered Discrete Fourier Transform-Spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDMA) is being discussed as an uplink multiple access scheme. In the 3GPP LTE standard, uplink transmission via one transmit antenna of a user equipment (UE) is supported. In the 3GPP LTE-A standard, in order to increase uplink transmission throughput, a UE performs uplink transmission (uplink MIMO transmission) via a plurality of transmit antennas.
As technology applicable to uplink MIMO transmission, there is a multi-stream or multi-layer transmission scheme of one UE for the purpose of spatial multiplexing, which may be referred to as a single user-MIMO (SU-MIMO) scheme. When such uplink SU-MIMO is applied, link adaptation for matching a modulation scheme, a coding scheme, etc. per an individual transmission stream or an arbitrary transmission stream group according to radio link condition may be applied. To this end, in order to apply different modulation and coding schemes (MCSs) to individual transmission streams (or transmission stream groups), multiple-codeword based transmission may be performed.
At this time, a receiver may determine whether errors occur in an individual codeword with cyclic redundancy check (CRC) and generate acknowledgement/negative acknowledgement information. If errors do not occur, a reception state is expressed by ACK and, if errors occur, a reception state is expressed by NACK. The receiver may transmit the generated acknowledgement/negative acknowledgement information to a transmitter so as to perform hybrid automatic repeat request (HARQ) transmission. HARQ transmission refers to a method of retransmitting previously transmitted data at a transmitter when receiving a NACK signal from a receiver and combining the previously received data and the retransmitted data at the receiver so as to improve retransmission performance.